... it would be really nice if the
serialization happened to be the 'standard' serialization for those without any
kind of wrapping at all,(no ( ) or no <xdm:wrapper> ..
etc)That way if you just happened to produce a single XDM Item of type
element or text there'd be no extra baggage.I think that would be really
cool.

It's worth pointing out that in the standard serialization, a
document node and its sole element child are indistinguishable in the serialized
output. So I don't think the goal of falling back to W3C serialization for some
subset of XDM sequences is achievable.